There has been suggested a method for etching a semiconductor wafer (hereinafter, referred to as “wafer”) in a processing chamber mainly by radicals in a plasma (see, e.g., PCT Publication No. 2013/175897). In the case of etching the wafer mainly by radicals, action of ions in the plasma on the wafer may need to be suppressed. Therefore, a partition plate for dividing an inner space of the processing chamber into a plasma generation space and a substrate processing space is provided inside the processing chamber. The partition plate suppresses passage of ions in the plasma from the plasma generation space to the substrate processing space.
On the other hand, the radicals in the plasma pass through the partition plate to reach the substrate processing space and contribute to the etching of the wafer. Therefore, the etching using radicals can be performed while suppressing approach of ions to the surface of the wafer. At this time, since the radicals reach the surface of the wafer without inactivation, an etching rate is increased. Accordingly, the etching process can be promoted. The inactivation of the radicals indicates that the radicals lose activity.
When the radicals are diffused and adsorbed onto the inner wall surface of the processing chamber and the components in the processing chamber, the adsorbed radicals are inactivated. Especially, when a distance between the wafer provided in the processing chamber and the inner wall of the processing chamber is short, it is easy for the radicals to be adsorbed onto the inner wall of the processing chamber, and the amount of inactivated radicals is increased. Thus, an etching rate becomes lower at an outer peripheral side than at an inner peripheral side of the wafer. Accordingly, in-plane uniformity of the etching deteriorates.